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Self-reported physical functioning was more influenced by pain than performance-based physical functioning in
Caroline B Terwee1, Rienk M A van der Slikke, Rob C van Lummel
1Institute for Research in Extramural Medicine, VU University Medical Center, van der Boechorststraat 7, Amsterdam 1081 BT, The Netherlands. cb.terwee@vumc.nl
Journal of Clinical Epidemiology
|June 13, 2006
Summary
Self-reported physical functioning is more affected by pain than performance-based functioning in knee osteoarthritis patients. This suggests the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) may lack content validity.
Area of Science:
- Orthopedics
- Rheumatology
- Rehabilitation Medicine
Background:
- Knee osteoarthritis significantly impacts patients' quality of life and physical function.
- Assessing physical functioning in knee osteoarthritis requires reliable and valid measurement tools.
Purpose of the Study:
- To investigate whether self-reported physical functioning is more influenced by pain compared to performance-based physical functioning.
- To evaluate the content validity of commonly used patient-reported outcome measures.
Main Methods:
- 163 knee osteoarthritis patients underwent performance-based (DynaPort KneeTest) and self-report (WOMAC, SF-36) assessments.
- Data were collected before, and 3, 6, and 12 months after knee replacement surgery.
- Correlation and factor analysis were used to compare measures of pain and physical functioning.
Main Results:
- Self-reported physical functioning showed higher correlations with pain (0.57-0.74) than performance-based functioning (0.20-0.26).
- Factor analysis indicated distinct loadings for self-report and performance-based measures.
- The relationship between performance-based and self-reported functioning strengthened post-surgery as pain decreased, particularly for the WOMAC.
Conclusions:
- The hypothesis that pain influences self-reported physical functioning more than performance-based functioning was supported, especially by the WOMAC.
- The findings suggest potential limitations in the content validity of the WOMAC regarding physical functioning assessment.
- Further research is needed to refine measurement tools for physical function in knee osteoarthritis.